Liquid crystal display panel and method for fabricating the same

ABSTRACT

A liquid crystal display panel and a method for fabricating the same are provided. The liquid crystal display panel comprises an active device array, a front substrate, at least one first spacer, and a liquid crystal layer. Wherein, the front substrate is disposed over the active device array. The first spacer is disposed between the front substrate and the active device array, and is partially embedded into an opening formed on the active device array. In addition, the liquid crystal layer is disposed between the front substrate and the active device array. Since the first spacer is embedded into the opening, the misalignment between the front substrate and the active device array can be effectively prevented, and the abnormal display due to the misalignment causing by external force can therefore be prevented.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a display apparatus and amethod for fabricating the same. More particularly, the presentinvention relates to a liquid crystal display panel and a method forfabricating the same.

2. Description of Related Art

As multi-media technology advances, a variety of semiconductor devicesor displays have been rapidly developed. The thin film transistor liquidcrystal display (TFT LCD) has such advantages as high resolution, highspace-effectiveness, low power consumption and no radiation, and hasbecome the main trend in this industry.

FIG. 1 is a cross-sectional view schematically illustrating aconventional liquid crystal display panel. Referring to FIG. 1, theconventional liquid crystal display panel 100 comprises a bottomsubstrate 110, an upper substrate 130, and a liquid crystal layer 120sealed by a sealant (not shown) between the bottom substrate 110 and theupper substrate 130. In addition, a cell gap d concerning the propertysuch as responding speed, contrast, and view angle of a liquid crystaldisplay is strictly controlled according to the optical property of theliquid crystal material. Specifically, the non-uniform cell gap d mayseriously affect the display quality and diminish the visibility ofimages. In general, spacers 102 are disposed between the bottomsubstrate 110 and the upper substrate 130 for maintaining the cell gapd.

Conventionally, the spacers 102 are formed during the fabricatingprocess of the upper substrate 130 and thus called ‘spacers on colorfilter’ (SOC). Since the spacers 102 is directly contacted with thebottom substrate 110 without any adhesion layer, a misalignment betweenthe upper substrate 130 and the bottom substrate 110 may occur asapplying an external transverse force F onto the liquid crystal displaypanel 100. Consequently, the display quality of the liquid crystaldisplay panel 100 is reduced.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a liquid crystaldisplay panel which has a uniform cell gap.

The present invention is also directed to a method for fabricating theliquid crystal display panel, for increasing the allowance of liquidcrystal and preventing the light leakage due to the misalignment of theliquid crystal display panel after being assembled.

The present invention provides a liquid crystal display panel,comprising an active device array, a front substrate, at least one firstspacer, and a liquid crystal layer. Wherein, the active device arraycomprises a substrate; a plurality of scan lines, disposed on thesubstrate; a plurality of data lines, disposed on the substrate, whereina plurality of pixel regions are defined by the scan lines and the datalines on the substrate, and the scan lines and/or the data lines have atleast one opening; a plurality of active devices, disposed in the pixelregions respectively and coupled to the corresponding scan lines and thecorresponding data lines; and a plurality of pixel electrodes, disposedin the pixel regions respectively and coupled to the correspondingactive devices. In addition, the front substrate is disposed over theactive device array. The first spacer is disposed between the frontsubstrate and the active device array and partially embedded into theopening. The liquid crystal layer is disposed between the frontsubstrate and the active device array.

According to an embodiment of the present invention, the first spacertakes a pillar shape.

According to an embodiment of the present invention, the liquid crystaldisplay panel further comprises at least one second spacer, which isdisposed between the front substrate and the scan lines and/or the datalines. In addition, the second spacer may take a pillar shape.

According to an embodiment of the present invention, the depth of theopening is less than the maximum elastic deformation of the secondspacer. For example, the depth of the opening may be less than 0.25 μm.

According to an embodiment of the present invention, the bottom area ofthe opening is at least two-thirds of the contact area between the firstspacer and the front substrate.

According to an embodiment of the present invention, the front substratecomprises a color filter.

According to an embodiment of the present invention, the active devicesare thin film transistors (TFT).

The present invention also provides a method for fabricating a liquidcrystal display panel. First, an active device array is provided. Theactive device array comprises a substrate, a plurality of scan lines, aplurality of data lines, a plurality of active devices, and a pluralityof pixel electrodes, wherein the scan lines and/or the data lines haveat least one opening. A plurality of pixel regions, in which the activedevices are disposed respectively, are defined by the scan lines and thedata lines on the substrate. Then, at least one first spacer and atleast one second spacer are formed on the front substrate. Next, aliquid crystal layer is formed on the active device array. After that,the front substrate is disposed over the active device array and thefirst spacer is partially embedded into the opening.

According to an embodiment of the present invention, the method furthercomprises a step of forming a sealant on the active device array todefine a liquid crystal injection region before forming the liquidcrystal layer.

According to an embodiment of the present invention, the front substrateis disposed over the active device array by performing the followingsteps. First, the front substrate is arranged over the active and thefirst spacer is aimed at the opening. Next, the active device array andthe front substrate are assembled. Then, the sealant is cured.

According to an embodiment of the present invention, the sealant can becured by ultraviolet or thermal.

According to an embodiment of the present invention, the active devicearray is a thin film transistor (TFT) array and the front substratecomprises a color filter.

According to an embodiment of the present invention, the active devicearray comprises a color filter on array (COA) substrate. In addition,the front substrate comprises a substrate and a common electrodedisposed thereon.

Since the opening is formed in the process of fabricating the scan linesand/or the data lines, the first spacer disposed on the front substratecan be partially embedded into the opening as assembling the liquidcrystal display panel. Therefore, the misalignment between the frontsubstrate and the active device array can be effectively prevented evenan external transverse force is applied on the front substrate. Thepresent invention resolves the problem of abnormal display due to themisalignment between the front substrate and the active device arraywithout any additional processing mask.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1 is a cross-sectional view schematically illustrating aconventional liquid crystal display panel.

FIG. 2 is a cross-sectional view schematically illustrating a liquidcrystal display panel according to one embodiment of the presentinvention.

FIG. 3 is a top view of an active device array 210 illustrated in FIG.2.

FIG. 4 and FIG. 5 are top views schematically illustrating active devicearrays of liquid crystal display panels according to other embodimentsof the present invention.

FIG. 6 is a cross-sectional view schematically illustrating a liquidcrystal display panel according to another embodiment of the presentinvention.

FIGS. 7A through 7D are schematic cross-sectional views showing afabricating process of a liquid crystal display panel according to oneembodiment of the present invention.

FIG. 8 is a three dimensional view schematically illustrating thesealant, which is disposed on the active device array as shown in FIG.7B.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers are used in thedrawings and the description to refer to the same or like parts.

FIG. 2 is a cross-sectional view schematically illustrating a liquidcrystal display panel according to one embodiment of the presentinvention. FIG. 3 is a top view of an active device array 210illustrated in FIG. 2. Referring to FIGS. 2 and 3, the liquid crystal200 comprises the active device array 210, a front substrate 220, afirst spacer 202, and a liquid crystal layer 230. Wherein, the activedevice array 210 may be a thin film transistor (TFT) array, whichcomprises a substrate 212, a plurality of scan lines 214, a plurality ofdata lines 216, a plurality of active devices 218, and a plurality ofpixel electrodes 219. The scan lines 214 and the data lines 216 aredisposed on the substrate 212, and defines a plurality of pixel regions217 on the substrate 212.

Referring to FIGS. 2 and 3, the data lines 216 has openings 204, whichare formed with the data lines 216 by the same process. Particularly,the distance between an opening 204 and the corresponding pixelelectrode 219 may be greater than 3 μm for preserving the aperture ratioof the liquid crystal display panel 200. In addition, the active devices218 may be thin film transistors. Each active device 218 is disposed inone of the pixel regions 217, and coupled to the corresponding scan line214 and the corresponding data line 216. The pixel electrodes 219 aredisposed in the pixel regions 217 and coupled to the correspondingactive devices 218 respectively.

Referring to FIG. 2, the front substrate 220 is disposed over the activedevice array 210. In this embodiment, the front substrate 220 may be acolor filter, which comprises a substrate 221, a plurality of colorfilter films 224, a black matrix (BM) 226, and a common electrode 228.Wherein, the color filter films 224 and the black matrix 226 aredisposed on the substrate 221 and covered with the common electrode 228.

Referring to FIG. 2, the first spacers 202 are disposed between thefront substrate 220 and the active device array 210. Wherein, the firstspacers 202 are partially embedded into the openings 204 respectively.It should be noted that, instead of ball shape spacers, the firstspacers 202 of the embodiment take pillar shapes for a more uniform cellgap, a higher light-transmittance, and a superior contrast.Particularly, the bottom area of each opening 204 is at least two-thirdsof the contact area between the corresponding first spacer 202 and thefront substrate 220, so as to fix the corresponding first spacer 202effectively.

Accordingly, the openings 204 are formed on positions, such as on thedata lines 216, which make no effect on the aperture ratio of the liquidcrystal display panel 200. Therefore, the abnormal display due to themisalignment between the active device array 210 and the front substratecaused by an external force applied on the liquid crystal display panel200 can be prevented. It should be noted that, in another embodiment asshown in FIG. 4, the openings 204 can be formed on the scan lines 214,which make no effect on the aperture ratio of the liquid crystal displaypanel 200 either. Furthermore, as shown in FIG. 5, the openings 204 canbe formed on both the data lines 216 and the scan lines 214.

FIG. 6 is a cross-sectional view schematically illustrating a liquidcrystal display panel according to another embodiment of the presentinvention. Referring to FIG. 6, the liquid crystal display panel of thepresent invention further comprises second spacers 206 for providingsuperior rigidity. Wherein, the second spacers 206 are disposed betweenthe active device array 210 and the front substrate 220. Specifically,the second spacers 206 are disposed between the front substrate 220 andthe scan lines 214 and/or the data lines 216.

It should be noted that the second spacers 206 are not embedded into theopenings 204 of the scan lines 214 and/or the data lines 216. It will beapparent to those skilled in the art that since the first spacers 202and the second spacers 206 are generally made of elastic material, thesecond spacers 206 deform and produce a difference in heights of thefirst spacers 202 and the second spacers 206, which is equal to thedepth h of the openings 204, as assembling the active device array 210and the front substrate 220. For preventing a plastic deformation of thesecond spacers 206 and an aggravation of the non-uniform cell gap of thedisplay panel 700, the deformation of the second spacers 206 should bewithin the range of an elastic deformation. In other words, the depth hof the openings 204 may be less than the maximum elastic deformation ofthe second spacers 206. For example, the depth h of the openings 204 isless than 0.25 μm as the maximum elastic deformation of the secondspacers 206.

Accordingly, after the liquid crystal display panel 700 has beenassembled, a difference in height is produced between the first spacers202 and the second spacers 206. Thus, forming the liquid crystal layer230 of the liquid crystal display panel 700 by the technique of one dropfill (ODF) improves the allowance of liquid crystal and preventsmisalignment as assembling the liquid crystal display panel 700. Aprocess of a liquid crystal display panel having spacers in differentheights is described in the following. Wherein, the active device arrayof the liquid crystal display panel may similar to those shown in FIG.3, 4 or 5. Though the active device array shown in FIG. 5 is selected asan example for the following description, there is no set limit on thepresent invention.

Referring to FIG. 5, an active device array 610 is provided first,wherein the active device array 610 may be a thin film transistor (TFT)array. The active device array 610 is substantially similar to theactive device array 210 shown in FIG. 3, besides a difference that boththe scan lines 214 and data lines 216 of the active device array 610have the openings 204. Therefore, a detailed description of the activedevice array 610 will not be repeated.

Then, referring to FIG. 7A, first spacers 202 and second spacers 206 areformed on a front substrate 220, wherein the first spacers 202 and thesecond spacers 206 may be made of elastic material. It should be notedthat the amounts of the first spacers 202 and the second spacers 206 arenot limited in the present invention, and the proper amounts can bedecided by those skilled in the art as preferred according to anecessary. In addition, the front substrate 220 may be a color filter asshown in FIG. 2. In this case, the first spacers 202 and the secondspacers 206 are formed over the black matrix 226 (as shown in FIG. 2),thus the aperture of the liquid crystal display is preserved.

Next, referring to FIG. 7B, a liquid crystal layer 230 is formed on theactive device array 610. It should be noted that a sealant 620 should beformed first to define a liquid crystal injection region 602 (as shownin FIG. 8) on the active device array 610 before forming the liquidcrystal layer 230. Thus, liquid crystal molecules 232 are filled intothe liquid crystal injection region 602 by the technique of one dropfill (ODF) to form the liquid crystal layer 230, which will sealedbetween the active device array 610 and the front substrate 220 in thefollowing process.

Afterwards, referring to FIG. 7C, the front substrate 220 is disposedover the active device array 610, wherein the first spacers 202 arecorresponding to the openings 204. Then, referring to FIG. 7D, the frontsubstrate 220 and the active device array 610 are assembled, and thefirst spacers 202 are partially embedded into the openings 204. Wherein,each second spacer 206 has a deformation equal to the depth h of theopenings 204. According to the embodiment mentioned above, the depth hof the openings 204 may be less than the maximum elastic deformation ofthe second spacers 206.

Specifically, due to the difference in heights of the first spacers 202and the second spacers 206 produced after assembling the active devicearray 610 and the front substrate 220, the allowance of liquid crystalincreases and can be applied to different structural designs. Theprocessing yields of the liquid crystal display panel can therefore beimproved. For example, for a 20 inch liquid crystal display panel, theactive device array 610 having openings 204 can increase the allowanceof liquid crystal in 20%.

After that, the sealant 620 is cured for fixing the relative positionsof the active device array 610 and the front substrate 220. Thus, theprocess for fabricating the liquid crystal panel is completed. Wherein,the sealant 620 can be cured by thermal or ultraviolet (UV) according tothe material property thereof. Since the following process of the liquidcrystal display panel 800 is apparent to those skilled in the art, adetailed description will not be repeated.

In summary, the present invention has at least the following advantages.

1. Openings are formed on the active device array for containing thefirst spacers on the front substrate after the liquid crystal displaypanel is assembled. Thus, the misalignment between the front substrateand the active device array can be effectively prevented even anexternal transverse force is applied on the front substrate. Theabnormal display due to the misalignment can therefore be prevented.

2. The scan lines and/or the data lines and the openings thereof areformed in the same process. In other words, the present invention formsthe openings on the active device array without any additionalprocessing mask.

3. The present invention disposes the first spacers and the secondspacers on the front substrate for improving the rigidity of the liquidcrystal display panel, wherein the first spacers are corresponding tothe openings. Due to the difference in heights of the first spacers andthe second spacers produced after assembling the active device array andthe front substrate, the allowance of liquid crystal increases and canbe applied to different structural designs. The processing yields of theliquid crystal display panel can therefore be improved.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

1. A liquid crystal display panel, comprising: an active device array,comprising: a substrate; a plurality of scan lines, disposed on thesubstrate; a plurality of data lines, disposed on the substrate, whereina plurality of pixel regions are defined by the scan lines and the datalines on the substrate, and the scan lines and/or the data lines have atleast one opening; a plurality of active devices, disposed in the pixelregions respectively and coupled to the corresponding scan lines and thecorresponding data lines; a plurality of pixel electrodes, disposed inthe pixel regions respectively and coupled to the corresponding activedevices; a front substrate, disposed over the active device array; atleast one first spacer, disposed between the front substrate and theactive device array and partially embedded into the opening; and aliquid crystal layer, disposed between the front substrate and theactive device array.
 2. The liquid crystal display panel according toclaim 1, wherein the first spacer takes a pillar shape.
 3. The liquidcrystal display panel according to claim 1, further comprising at leastone second spacer, disposed between the front substrate and the scanlines and/or the data lines.
 4. The liquid crystal display panelaccording to claim 3, wherein the second spacer takes a pillar shape. 5.The liquid crystal display panel according to claim 3, wherein the depthof the opening is less than the maximum elastic deformation of thesecond spacer.
 6. The liquid crystal display panel according to claim 5,wherein the depth of the opening is less than 0.25 μm.
 7. The liquidcrystal display panel according to claim 1, wherein the bottom area ofthe opening is at least two-thirds of the contact area between the firstspacer and the front substrate.
 8. The liquid crystal display panelaccording to claim 1, wherein the front substrate comprises a colorfilter.
 9. The liquid crystal display panel according to claim 1,wherein the active devices are thin film transistors (TFT).
 10. A methodfor fabricating a liquid crystal display panel, comprising: providing anactive device array, which comprises a substrate, a plurality of scanlines, a plurality of data lines, a plurality of active devices, and aplurality of pixel electrodes, wherein the scan lines and/or the datalines have at least one opening, and a plurality of pixel regions, inwhich the active devices are disposed respectively, are defined by thescan lines and the data lines on the substrate; forming at least onefirst spacer and at least one second spacer on the front substrate;forming a liquid crystal layer on the active device array; and disposingthe front substrate over the active device array and partially embeddingthe first spacer into the opening.
 11. The method according to claim 10,further comprising forming a sealant on the active device array todefine a liquid crystal injection region before forming the liquidcrystal layer.
 12. The method according to claim 11, wherein the stepsof disposing the front substrate over the active device array comprise:arranging the front substrate over the active and aiming the firstspacer at the opening; assembling the active device array and the frontsubstrate; and curing the sealant.
 13. The method according to claim 12,wherein the sealant is cured by ultraviolet or thermal.
 14. The methodaccording to claim 10, wherein the active device array is a thin filmtransistor (TFT) array and the front substrate comprises a color filter.